Bryophytes on Brazilian ironstone outcrops: Diversity, environmental filtering, and conservation implications

Brazilian ironstone outcrops (“Cangas”) are characterized by high soil iron concentrations, high ambient temperatures, strong water restrictions, and occupation by vascular plants showing high levels of rarity and/or endemism. Another group of plants commonly inhabiting Cangas are bryophytes, which have important roles in maintaining soil moisture and nutrient levels, but are only infrequently investigated. Cangas sites are currently threatened by mining, uncontrolled urbanization, and deforestation. We therefore addressed the following questions: 1) What is the beta diversity of bryophyte communities on ironstone outcrops in two different Protection Areas - PAs? 2) Does anthropogenic disturbance drive bryophyte community assembly? 3) What are the influences of microhabitats and substrate availability on bryophyte assemblages? We analyzed the bryophytes in eight Cangas sites in two PAs in Minas Gerais State, Brazil, and characterized their communities in terms of their different microhabitats/substrates, elevation, and disturbance levels. Ninety-six bryophyte species were identified (56 mosses, 40 liverworts), distributed mainly among Tree-Associated microhabitats (68 spp.) and Tree Bark substrates (67 spp.). Bryophytes demonstrate deterministic distributions and the anthropogenic disturbance is an important environmental filter. We also identified differentiation in bryophyte assemblages among the different microhabitats/substrates on ironstone outcrops, especially in Gandarela National Park sites (GA). In Rola-Moça State Park (RM), there was a taxonomic homogenization, probably associated with high levels of anthropogenic disturbance. Compared to other plant communities encountered growing on different types of rocky outcrops, the ironstone outcrops in southeastern Brazil were found to harbor high bryophyte diversity. These findings highlight the importance of conserving diverse Cangas sites, as they accommodate specific bryophyte communities.